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Clear Cached Memory on Ubuntu

Terminal - Clear Cached Memory on Ubuntu
sudo sync && sudo echo 3 | sudo tee /proc/sys/vm/drop_caches
2012-03-17 08:27:58
User: StephenJudge
Functions: echo sudo sync tee
-2
Up
Down
Clear Cached Memory on Ubuntu

"That's it. Not much to see here. The first command writes any cache data that hasn't been written to the disk out to the disk. The second command tells the kernel to drop what's cached. Not much to it. This invalidates the write cache as well as the read cache, which is why we have the sync command first. Supposedly, it is possible to have some cached write data never make it to disk, so use it with caution, and NEVER do it on a production server. You could ... but why take the risk?

As long as you are running a post 2.6.16 kernel,..."

Source: http://ubuntuforums.org/showpost.php?p=3621283&postcount=1

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Alternatives

There are 4 alternatives - vote for the best!

Terminal - Alternatives
free && sync && echo 3 > /proc/sys/vm/drop_caches && free
2009-08-05 23:44:34
User: ricardoarguello
Functions: echo free sync
32
Up
Down
Release memory used by the Linux kernel on caches

The Linux kernel uses unused memory in caches. When you execute "free" you never get the "real" available memory.

Show sample output | Comments (4) | Add to favourites | Report as malicious
sync && echo 1 > /proc/sys/vm/drop_caches
2011-06-10 07:32:28
User: KeePon
Functions: echo sync
Tags: memory ram kernel sync cache free
17
Up
Down
clean up memory of unnecessary things (Kernerl 2.6.16 or newer)

run sync first to flush useful things out to disk!!!

To free pagecache:

echo 1 > /proc/sys/vm/drop_caches

To free dentries and inodes:

echo 2 > /proc/sys/vm/drop_caches

To free pagecache, dentries and inodes:

echo 3 > /proc/sys/vm/drop_caches

Show sample output | Comments (0) | Add to favourites | Report as malicious
sync; echo 3 | sudo tee /proc/sys/vm/drop_caches
2010-05-23 11:39:35
User: bandie91
Functions: echo sudo sync tee
7
Up
Down
clean up memory on linux

where proc filesystem mounted under /proc

Show sample output | Comments (5) | Add to favourites | Report as malicious
sync && echo 3 | sudo tee /proc/sys/vm/drop_caches
2011-10-18 15:22:25
User: mariusbutuc
Functions: echo sudo sync tee
Tags: cache
6
Up
Down
Clear filesystem memory cache

Found here: http://ubuntuforums.org/showthread.php?t=589975

Comments (0) | Add to favourites | Report as malicious
/sbin/sysctl -w vm.drop_caches=3
2012-08-05 22:09:04
User: jlaunay
4
Up
Down
Release memory used by the Linux kernel on caches

=1 --> to free pagecache

=2 --> to free dentries and inodes

=3 --> to free pagecache, dentries and inodes

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Know a better way?

If you can do better, submit your command here.

What others think

Funny trick, but yes never use it on any prod machine. There can be so much set in cache between the two commands, that it looks like naked free fall.

Comment by makidoko 61 weeks and 2 days ago

Your point of view

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